An electronic instrument as typified by an electronic piano conventionally includes a pair of musical sound signal generation means for generating two musical sound signals for one key operation (key-on) for stereo performance. If such pair of musical sound signal generation means are provided as much as the number of the keys, musical sound signals for sound production can be securely generated. However, the increase in number of the musical sound signal generation means accompanies the increase in costs as well.
Therefore, the applicant has developed a musical sound signal generation apparatus to effectively utilize the musical sound signal generating means as disclosed in the Unexamined Japanese Patent Publication No. 10-49159. Teaching of this Publication is that if a new key-on is made when all the musical sound generation means are in use, two pairs of the oldest musical sound signal generation means in order of sound production are selected from all the musical sound signal generation means in the sounding mode, and one of the musical sound signal generation means constituting each pair is truncated (rapidly attenuated), while the remaining musical sound signal generation means operate as they are. Thereby, since two musical sound signal generation means are changed into the silent mode (become free), they can be reused as the musical sound signal generation means for generating musical sound signals in stereo sounding, corresponding to a fresh key-on.
However, in case of the musical sound signal generation apparatus of the above Publication, when all of the musical sound signal generation means are in use and that the oldest musical sound signal generation means in order of sound production is generating one of the musical sound signals which constitute a chord (for example, a chord consisting of 3 or 4 different tones), if this musical sound signal generation means is silenced and reused as the musical sound signal generation means for stereo sounding corresponding to a fresh key-on, there is a fear that the players and/or the audience may feel uncomfortable for lack of the sound in the chord.